Expose timer queue impls unconditionally, support timer queue items stored outside of tasks (e.g. RTOS-aware block_on)

[bugadani]

This PR is a backwards-compatible implementation that allows HAL implementers to mix queue implementations, which allows users to mix executors. This is mainly targeted at RTOS implementations which can use embassy-executor, and also provide their own block_on implementations simultaneously.

[Copilot]

Pull request overview

This PR enables mixing of timer queue implementations in embassy-time-queue-utils, allowing HAL implementers to support both embassy-executor and custom RTOS block_on implementations simultaneously. The changes expose both integrated and generic queue implementations unconditionally while maintaining backward compatibility through a feature-gated default.

• Extracted schedule_wake_queue_item method from schedule_wake to support external timer queue item storage
• Made both queue implementations (queue_generic and queue_integrated) publicly available regardless of feature flags
• Introduced a wrapper Queue struct that delegates to the appropriate implementation based on feature configuration

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
embassy-time-queue-utils/src/queue_integrated.rs	Refactored schedule_wake to delegate to new schedule_wake_queue_item method, enabling queue item storage outside of executor tasks
embassy-time-queue-utils/src/lib.rs	Removed feature-gating on queue module exports, added wrapper Queue struct that provides a unified interface while delegating to the feature-selected implementation
embassy-time-queue-utils/CHANGELOG.md	Documented the new public API changes and added entry for schedule_wake_queue_item method

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[lulf]

No objection from me :)